Temporary living facilities such as hotels and motels and, in some cases, apartments are commonly provided with heating and air conditioning systems for the comfort of their guests and those systems have traditionally been operated on an "overuse" basis, i.e., they were "on" most of the time on the assumption that it is better to leave them on than to have the guests uncomfortable, and cheaper than to have employees turning them off and on when guests leave or arrive. They are commonly thermostatically controlled so that room temperatures are between desired limits, but no special effort was made to deactivate the supply of heat or a cooling medium to an unoccupied room.
More recently, with the increased awareness of fuel shortage and the increased cost of energy, efforts have been made to induce patrons of such establishments to voluntarily turn off air conditioning units or heating systems whenever they left their rooms unoccupied. While this has had some beneficial impact, guests tend to ignore requests of this type for various reasons.
Other efforts have therefore been made to render the deactivation of the heating or cooling systems less voluntary, and to make use of those systems more efficient. One example of such system is found in U.S. Pat. No. 4,060,123, Hoffman et al., in which a thermostatically controlled system is operative to control the room temperature within the normal comfort range only when the guest inserts his room key, or some other unique, recognizable identifier unto a lock switch or the like. The theory behind this patent seems to be that the system need only operate when the room is occupied and that the room will be occupied when, and only when, the key is available for insertion into the lock switch.
While the goal of operating the system only when the room is occupied is a laudable one, it will be apparent that the Hoffman et al., system can be easily defeated whenever more than one key (or other identifier) is distributed. It is also undersirable because it required an extra activity on the part of the guest.
Another system is shown by Curatolo in U.S. Pat. No. 4,091,866 in which the H/AC system is controlled on the basis of opening and closing the door giving access to the room. This is, of course, only usable under special conditions and presents the problem of having to have the door lock in a special condition.
In either of these systems, room occupancy is not determined directly but, rather, inferred from the state of devices in or associated with the room. Other systems directed generally to energy conservation in the control of H/AC systems are shown in the following U.S. Pat. Nos.
1,597,773-Dodge PA1 2,655,806-Stiler PA1 3,188,618-Rentz PA1 3,352,490-Dalzell et al. PA1 3,529,214-Corn PA1 3,934,797-Perlmutter PA1 3,984,699-Bailey